Republican presidential contender Ted Cruz has tapped former technology executive Carly Fiorina as his running mate in the race for the White House.
The Texas senator plans to formally unveil his pick for vice president at an event in Indianapolis.
Mr Cruz is trying to generate momentum for his struggling campaign. GOP front-runner Donald Trump swept primaries in five North eastern states on Tuesday.
Mr Cruz has been mathematically eliminated from winning enough delegates to clinch the Republican presidential nomination before primary voting ends.
But he is pushing to claim the nomination at a contested national convention in July.
The 61-year-old Fiorina endorsed Mr Cruz earlier in the year after abandoning her own presidential bid.
The former chief executive at Hewlett-Packard has never held elected office.
"Of all the people who didn't make it far in the race, she was one of the best about laying out her plan, talking about who she is and her accomplishments," said Doug De Groote, a fundraiser for Mr Cruz based near Los Angeles.
It was an unusual move for a candidate who is far from becoming his party's presumptive nominee, but Mr Cruz is desperate to generate momentum for his struggling campaign.
Some Cruz allies praised the selection of Ms Fiorina, but privately questioned if it would change the trajectory of the race.
Mr Trump has won 77% of the delegates he needs to claim the nomination, and a win next week in Indiana will keep him on a firm path to do so.
Mr Cruz is set to appear with Ms Fiorina in Indiana's capital city, having staked his candidacy on a win in the state's primary contest next Tuesday. Ms Fiorina's California ties could also give Mr Cruz a big boost in that state's high-stakes primary on June 7.
"Carly has incredible appeal to so many people, especially in California," Mr De Groote said. "She can really help him here."
Her first major foray into politics was in 2010, when she ran for Senate in California and lost to incumbent Sen Barbara Boxer by 10 percentage points.
Mr Trump criticised a Fiorina pick as "ridiculous" and "dumb" even before it was announced.
"First of all, he shouldn't be naming anybody because he doesn't even have a chance," the New York billionaire said in an interview on Fox News.
"Naming Carly's dumb, because Carly didn't do well. She had one good debate - not against me by the way, because I had an unblemished record of victories during debates - but she had one victory on the smaller stage and that was it," Mr Trump said.
He added, "She's a nice woman. I think that it's not going to help him at all."